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Microbes and Food: A Menu of Microbial Delights |
Chapter: 10
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The Color of Olives In certain cultures, the olive tree is a symbol of life, and the olive branch a symbol of peace ("extending an olive branch" to someone indicates you wish peace). It is discouraging that the natural fruit of the respectable olive tree should taste so bitter. Tradition, bacteria, and the fermentation process, however, solved that problem long before the chemistry was understood. In Western Europe, especially Spain, ancient people harvested the olives while still green and soaked them in lye (sodium hydroxide) to neutralize the bitterness. The olives were then washed, covered with salt solution, and set in the sun in small casks to ferment. The result, some weeks later, was the Spanish, or green, olive. Another type of olive, the black olive, originated in Greece and was popular in Eastern Europe. In this case the olives were allowed to ripen on the tree and assume a pale red color. Treatment in lye was accompanied by aeration, and the oxidation of phenolic compounds called tannins left black deposits in the olive skin. The olives were not fermented and had to be eaten quickly before they spoiled. Even today, Greek olives must be pasteurized or treated with preservatives in packaging. The Italians modified Greek olives still further. They allowed black olives to ferment in large quantities of salt, a process that not only sharpened the taste of the olive but also drew out the water. The wrinkled olives are the familiar Sicilian olives. |
